Duplex socket contact with breakoff tab



' Sept. 16, 969 R. L. MARTIN 3,

DUPLEX socxm comm wmx BREAKOFF TAB Filed Nov. 3, 1966 3 Sheets-Sheet 1INVENIOR Rater? L fill/'14}:

ATTORNEY R. L. MARTIN Sept. 16, 1969 3 Sheets-Sheet 2 Filed Nov. 3. 1966m n T .0 r 0N a m u m r M a A W 0 e 1D a R Sept. 16, 1969 R. L. MARTIN3,467,941

DUPLEX SOCKET CONTACT WITH BREAKOFF TAB Filed Nov. 5, 1966 3Sheets-Sheet 5 INVENTOR. Baker? 1. Maria:

m Mew United States Patent US. Cl. 33931 5 Claims ABSTRACT OF THEDISCLOSURE A duplex grounding outlet is provided having electric contactstrips adapted to split circuit Wiring by removal of a breakotf tab fromeach strip to permit separate power supply to each half of the duplexoutlet. The breakotf tab is provided in readily accessible and easilyseverable combination with the housing.

This invention relates to a grounding outlet having multiplespring-biased fastening means for providing electrical engagement withinserted line wires. More specifically, it relates to a duplex plugreceptacle having a pair of electrical line contacts each formed from ablank piece of sheet material and having a breakoff means readilyremovable from the exterior of the receptacle whereby each contact maybe made in two separate pieces. Each of these can be connected for asplit circuit wiring.

The invention contemplates an improvement over the device disclosed inUS. Patent No. 3,339,170 of Robert Martin and assigned to the sameassignee, and from which this application forms a continuation-in-part.As disclosed in the Martin patent, a plurality of breakolf tabs areprovided for each line contact, whereby each contact can be made intotwo separate pieces. Each separate piece, therefore, can be connected totwo wires of different sizes for split circuit wiring.

The breakotf tabs for each contact are preformed after the line contactis formed thereby providing a weakened portion between each of thebreakolf tabs and its associated line contact.

Although a number of convenience outlet designs exist which provide abreakoff tab which is readily accessible from the exterior longitudinalsides of the device, these are characterized in having a contact stripwhich is largely vertically dispose-d relative to the longitudinal sidesof the outlet structure. No device has been available heretofore whichhas a horizontally disposed contact strip, i.e. one lying parallel inthe circuit wire connecting and circuit separation portions and whichhas a breakoff tab readily accessible from the external longitudinalside of the device.

Of particular importance in this respect is the provision of a contactstrip which lies parallel to the back of the outlet structure so thatwire fasteners may be provided which also lie essentially parallel tothe back of the device and which are activated by pushing wires into thefasening structure as explained more fully in Patent No. 3,339,- 170,referenced above.

It is an object of this invention to provide a convertible plugreceptacle having a line contact which is parallel to the back of thedevice and which is provided with a breakolf tab accessible from thelongitudinal side of the device to permit separation of the contact intotwo separate pieces for a split circuit wiring.

It is another object of this invention to provide a line contact memberfor an electrical outlet device which utilizes an economy of material inits construction.

It is a further object of this invention to provide a duplex receptacleplug having breakotf tabs integral with their associated line contactswhich are at all times conveniently accessible to removal.

3,467,941 Patented Sept. 16, 1969 It is still another object of thisinvention to provide a sturdy duplex plug receptacle which confineswithin its exterior outlines the breakolf portions of the line contactmembers but which make the breakoff portions readily accessible to agripping tool.

Additional objects and advantages will be in part ap parent and in partpointed out in the description which follows.

In one of its broader aspects the objects of the invention may beachieved by providing a duplex convenience outlet device adapted tosplit circuit wiring which comprises an insulated housing including abase and cover, elongated cavities in said base, said base cavitieshaving disposed against the bottom thereof contact strips, said contactstrip being adapted to receive at each end section thereof a line wireand a power blade in electrical connection therewith, and said striphaving between said two end sections a breakolf tab integral with andextending laterally beyond the boundary of said end sections, the outerwall of each cavity in the base being formed with a side opening toprovide access of a gripping tool to said breakoff tab, said cavitiedbase having a positioning boss formed therein to maintain separation ofsaid end sections, and said cover having depending ribs to prevent thesections from rising above said positioning boss.

In one of its preferred embodiments, an electric outlet is provided foruse with a grounding attachment plug to have a grounding contact and twoU-shaped line contacts, each U-shaped line contact having at theterminus of each end section prong-receiving means and having providedin the base of each end section two separate cam arrangements forengaging two separate wires in a spring lock arrangement in the base ofeach contact end section.

To provide the four separate cam arrangements of the integral contact,the line contacts are formed from metal strip having good leaf springproperties and the strip is trifurcated at two longitudinal portions ofthe base of the line contact so as to form three parallel prongs or legsextending lengthwise of the contact. One end of each of the outer legsis made free of the base so as to form a cantilever cam leg. The twoouter cam legs in combina tion with the central leg and the portion ofthe strip which joins the three legs at their held end comprises an Eform which is integrated into each end section of the contact as onecomponent element thereof.

Each of the cam legs may be up from the base of the U-shaped contact sothat a wire may be pushed through an opening in the base in registrywith the bent up end of the cam leg. A wire may thus be engaged in thebase of the contact between the free movable end of the cam leg and theremaining edge or shelf of the contact base from which the free end wasdisplaced as described more fully in US. Patent No. 3,339,170,referenced above. An inserted wire is electrically contacted on one sideby the shelf and on the other side by the free end of the leg. Fourwires, therefore, can be individually held in firm engagement with eachU-shaped line contact.

Each line contact is provided with a breakoff tab defined in part by aprotrusion extending beyond one longitudinal edge of the strip and inpart by a plurality of spaced-apart slots extending from the outerlongitudinal edges of the contact between the contact end sections andmore specifically between the E forms, and extending to the middleportion of the contact. By removing the breakotf tab each end section ofthe strip can be made into a separate contact which can be connected totwo wires of different sizes for a split circuit wiring.

The line contacts are enclosed within an insulating housing which isformed by two molded insulating members. One of these members, a base,is provided with a pair of cavities or recesses each of which snuglyreceives one of the U-shaped contact strips. Each recess is providedwith an opening in the middle portion through its outer side wall tothereby allow access to the breakoff tab on the contact strip forremoval by bending it back and forth by movement of a gripping tool inthe side opening of the housing.

Additional advantages and details believed to be novel in the article ofthis invention will become apparent from the following description andclaims taken with the accompanying drawings, wherein:

FIG. 1 is a perspective view in elevation of a con venience electricaloutlet or receptacle utilizing the principles of this invention;

FIG. 2 is a side elevational view of the electrical receptacle shown inFIG. 1;

FIG. 3 is a bottom view of the receptacle shown in FIG. 2;

FIG. 4 is a cutaway of the base portion of the plug receptacle showingthe arrangement of contact strips;

FIG. 5 is a detailed perspective view of one of the contact stripsaccording to the principles of this invention;

FIG. 6 is a detailed perspective view of a contact such as shown in FIG.5 but in severed formation;

FIG. 7 is a perspective of a preform of a contact in layout formaccording to the principles of this invention;

FIG. 8 is a perspective view partially broken away of a cover portion ofthe receptacle shown in FIG. 1;

FIG. 9 is a plan view of the cover portion shown in FIG. 8;

FIG. 10 is an enlarged perspective view of a portion of FIG. 3illustrating the means of assembly of a contact strip in the baseportion of the receptacle according to this invention;

FIG. 11 is a perspective view of a modified form of the receptaclestructure as shown in FIG. 1;

FIG. 12 is a side elevation of the device of FIG. 11;

FIG. 13 is an exploded perspective view of the inverted device toillustrate the bottom exterior of the base and the internals of thecover of the receptacle of FIG. 11; and

FIG. 14 is a sectional view of the device of FIG. 12 taken along theline 14-14 of FIG. 12.

With reference to FIG. 1, it will be seen that a grounding outletreceptacle constructed in accordance with the principles of thisinvention comprises a molded cover 2 having prong receptacles 4 andgrounding receptacles 6, a mounting bracket 10 and a base portion 12.The base portion 12 comprises side walls 14 in each of which a sideopening in the form of a vertical slot 16 extends part way through thebase 12 as best shown in FIGS. 2 and 3. The slot 16 is bordered by ribmembers 18, the function of which will be explained later. As shown inFIG. 4, the base 12 houses a pair of U-shaped contact strip members 26in longitudinal parallel recesses divided by an insulating center wall20.

Since each of the line contacts 26 is identical, reference will be madeto only one. It will be seen that the line contact is formed from asingle strip of metal, preferably of spring tempered brass, and isgenerally of a shallow U-shape, as best shown in FIG. 5. The base of theU- shaped contact is generally rectangular in shape with two spacedportions of the base trifurcated so as to form two pairs of identicalcam legs 28. The legs 28 are each out free of the base at one end andpartially bent so as to form cantilever cams 30. A channel (not shown)may be coined in the center of each of the legs 28 extending the lengthof the leg to add strength to the cantilever cam legs. Central leg 32separates the cam legs 28 from each other and mechanically joins theirheld ends to a central portion 34.

The breakofi tab at the central section of the contac strip is partlydefined by a plurality of transversely extending slots 38, 40 defining abreakolf tab 42, the tab also being partially defined by extending tabend extending beyond the longitudinal edge of the remainder of the Ncontact strip. The purpose of forming two separate contact pieces fromeach contact strip 26 is to permit split circuit wiring. The slots 38extend from the outer longitudinal edge of the base toward the middleportion thereof and the slot 40 extends from the opposite outer edge tothe area between the slots 38. With this arrangement the breakoff tab 42may be removed from the strip as by bending back and forth and/ortwisting the weakened portions 36 to become sheared along the centralaxis of the line contact 26 as best shown in FIG. 6. It is importantthat the breakolf portions be internally of the longitudinal stripboundaries so as to provide for ample leverage in manipulating the tabwith a gripping tool until it is severed. Each upwardly extending arm ofthe U- shaped contact is formed to provide prong-receiving legs 44, 46which are bifurcated portions of the contact strip 26. Legs 44, 46 areperpendicular to each otherand provide a double wipe arrangement forengaging the prong of a connector.

Referring now to FIG. 7, the U-shaped contact 26 is shown in layout formand is seen to be of a generally rectangular strip form. It will be seenthat the outwardly extended portion of the breakofi tab 42 has the samedimensions as the slot 40 extending inwardly from the opposite outeredge of the adjacent strip contact 26. The slot 40, which functions as apositioning means to be more fully described below, is formed by removalof metal for the breakoff tab of an adjacent contact strip during thecutting operation on appropriate sheet metal. With this arrangement asingle die can be used for cutting a plurality of contact strips and theamount of waste metal is thus minimized by the effective transfer ofmetal from one contact strip to an adjacent strip.

Referring now to FIGS. 8 and 9, the positioning of the contacts 28 withrespect to the molded cover 2 will be understood. One of the contacts 28is shown mounted on the cover 2, while the other contact has beenremoved to better show the internal structure of the cover 2.Furthermore, in the duplex-type plug receptacle or outlet which isshown, the contacts are positioned symmetrical with respect to aperpendicular axis drawn through the center of the outlet and extendingin a direction parallel to the length of the outlet. Since the overalldevice is symmetrical about such longitudinal axis, only one contact andits associated supporting structure will be discussed. The cover 2 isprovided with an elongated rib 52 extending in the direction of thelonger dimension of contact strip and upon which rests the center legs32 of the contact strip. The elongated rib also serves as an insulatingbarrier between the cam legs 28. Each of the prong-receiving legs 44, 46is snugly received in slots 48, 50 which terminate into the apertures 4provided in the cover respectively for the insertion of prongs forengaging legs 44, 46. On bothsides of the elongated ribs 52 are formedidentical shelf portions 60. Each of these shelf portions is providedwith a wire-receiving bore 58.

Adjacent the central outside portion of each rib 52 is a depending legmember 56 having an upper positioning section which occupies the slot 16in the base 12 and a lower rectangular block section 54 which extendsslightly below the rib 52. When the cover and base are assembled, thebottom surface of the block 54 of depending leg 56 rides on that portionof the breakoff tab within the outside longitudinal edge of the contactstrip. By this riding action the breakoif tab is biased at or slightlybelow the plane of the contact strip and in effect when the tab 42 isremoved can occupy the area previously occupied by parts of the breakotfportion 36 and the breakoff tab 42.

A-grounding contact 62, shown positioned on the cover 2, is providedwith two double wipe prong-engaging portions 70. A mounting bracket 10,which is provided with the usual mounting means at either end, ispositioned on the molded cover in abutting relationship with the groundcontact 62 and an insulated relation between the contacts 28. The moldedbase 12 is placed over the contacts 28 and the mounting bracket 10.

Referring now to FIG. 4, it will be seen that the base 12 is providedwith an insulating wall or barrier which extends lengthwise of the baseand divides the base into two pockets each of which has a rectangularshape conforming to that of the base of the U-shaped line contacts 26.As shown in FIG. 10, the contact sits on the base 12 and adjacent thebarrier 20. A positioning member 64, which also acts as an insulatingmember, projects from the barrier wall 20 as a right-angle rib member 68which is adapted to fit in the lower narrower portion of the groove incontact 26. As seen in FIG. 1, the breakoff tab 42 of the contact 26extends to the ribbed edges 18 of the slot 16 in the side wall 14. Theribbed edges provide protection against the breakoif tab from contactwith external objects and thus prevent shorting before the tab isremoved. As shown in FIG. 3, the slot 16 extends into the base portionapproximately to the central axis of the contact strip. It will be seenthat the breakolf portions 36 lie approximately along this axis. Thus,the ribbed right-angle positioning member 68, the breakoif portions 36and the edge of the slot 16 are all generally located on the same axis.This allows the breakofi tab 42 to be moved or gripped by a suitabletool through the slot 16 thus causing the weakened portions 36 to besevered approximately along the central axis of the line contact 26.With this arrangement the severed portions 36 are separated by theinsulating rib section 68 as well as being confined within the interiorof the housing. Further, the depending member 54 now occupies the Spaceleft by the breakoff tab, thus completing the insulating barrier betweenthe cross pieces 34.

The base 12 is provided with eight identical holes 22 through whichwires are inserted to be engaged by the cam legs 28 in the line contactportion of contact strip 26. The free ends of the cam legs 28 extendwithin the projection of the holes 22 and the wire-receiving recesses 58in the cover 2. A wire, upon being inserted in a hole 22, may firstengage the shelf 60 and may be deflected by it to engage the inclinedsurface of the free end of cam leg 28 as it is further inserted. As thewire is inserted in the hole 22 and pressed against the free end of thecam leg 28, the cam leg is deflected in cantilever fashion throughoutits length thereby providing a spring bias force on the side of the wireand securing it within the recess 58. With this construction theinsertion of a wire in the spring lock fastening means not only causesdeflection of the yieldable cam legs 28, but also causes a torsionaldeflection or yielding of the center legs 32 which aids in providing aspring bias force upon the wire. Rectangular apertures or access holes24 are provided for the insertion of a tool to release the pressure lockwire fastening means. A tool such as a screwdriver (not shown) may beinserted through a rectangular aperture 24 and is brought to bear on thecam leg 28 thereby deflecting the cam leg away from the wire andreleasing the wire.

After the wiring device is assembled and each breakofl tab 42 issubsequently removed in the manner described above, the separate endsections of each contact strip 26 are firmly held in place during andafter removal of the breakoff portions by the cooperation of the rightangle rib member 68, the elongated rib 52 and the slots 48, with theirrespective portions of the line contact strip 26.

Although several embodiments of the invention have been depicted anddescribed, it will be apparent that these embodiments are illustrativein nature and that a number of modifications in the apparatus andvariations in its end use may be effected without departing from thespirit or scope of the invention as defined in the appended claims.

One such modification is illustrated in the structure illustrated inFIGURES 11 through 14.

Referring now to these figures a form of the convenience outletstructure is shown which is preferred for use where a device of greaterstrength is desired without an attendant loss or sacrifice of theconvient accessibility and removability of the breakoif tab.

In the description which follows emphasis is placed on those portions ofthe device which are distinct from those shown and described withreference to FIGURES 1 through 10. The contact strip incorporated in thedevice of FIGURES 11 through 14 can be identical for example, with thatdescribed earlier and its description is not repeated here. Further thedescription given for the device of FIGURES 1 through 10 is not repeatedfor the portion of the insulating housing which is the same as that ofthe device shown in FIGURES 11 through 14.

The grounding contact 162 of FIGURE 13 is the same in essence as thegrounding contact of FIGURE 9.

The greater strength of the device of FIGURES 11 through 14 isattributable to the bridge which joins the side wall portions 72 to adda strength feature to the outer walls of the insulating base 112. Thisstrength is beyond that added by the rib structure 18 of the device asseen in FIGURE 1.

The tab 142 is seen from the figures to be readily accessible to agripping tool shown in phantom in FIG- URE 11, and the cavity 116 in thelower portion of the side wall 72 is large enough to permit the grippingtool to articulate the tab and to cause it to sever at its joint withthe contact strip.

Further it is evident particularly from FIGURE 13 that the protrusion ofthe tab 142 beyond the longitudinal boundary of the remainder of thecontact strip does not create an assembly problem in inserting the stripinto the base 112 of the insulation housing inasmuch as the clearance 71on the inside of the bridge permits the contact strip to be insertedinto its pocket in the base 112 without being bent or turned orotherwise maneuvered into place.

The cover 102 of the device is essentially the same at its upper portionas that of FIGURE 1 with the exception that a pair of ears 103 areprovided as lids for the bridges '70 protruding in conforming fashionfrom each side of the device.

The lower or depending portion of the cover is also distinct in certainrespects described below as ay be seen by comparison of FIGURES 8 and13. In particular the depending leg member 56 of FIGURE 8 has nocounterpart in the structure of the cover 102. The other dependingportions 150, 158, and 154 have functions described with reference tothe similarly numbered parts of the device of FIGURE 8.

What is claimed is:

1. A duplex convenience outlet device adapted to split circuit wiringwhich comprises an insulated housing including a base and a cover, apair of elongated cavities in said base, said cavities having disposedagainst the bottom thereof electric contact strips, each contact stripbeing adapted to receive at each end section thereof a line wire and apower blade in electrical connection therewith, and said strip havingbetween said two end sections a breakofl tab integral and substantiallyin the plane with and extending laterally beyond an edge of said strip,the outer wall of each cavity in the base being formed with a sideopening to provide access of a gripping tool to said breakoff tab, eachcavity of said base having a positioning boss disposed opposite saidopening to maintain separation of said sections, and said cover havingdepending bosses to prevent the sections from rising above saidpositioning boss.

2. The device of claim 1 in which the line wire connection is through apair of separate push-in connectors in each end section.

3. The device of claim 1 wherein the side opening is formed below anintegral outwardly extending bridge connecting the wall portions abovesaid opening.

7 8 4. The device of claim 1 having a tab and a slot on 2,974,301 3/1961Slater 33914 the opposite edge equal in depth to the extent of pro-3,339,170 8/1967 Martin 339-14 XR trusion of said tab.

5. The device of claim 1 wherein each breakoff tab RICHARD E. MOORE,Primary Examiner extends from between the bottom of said cavity and said5 PATRICK A CLIFFORD, Assistant Examiner depending boss.

References Cited UNITED STATES PATENTS 2,969,518 1/1961 Slater.

US. Cl. X.R.

